Thirty Meter Telescope (TMT)

The Thirty Meter Telescope (TMT) is a proposed extremely large telescope with a 30-meter primary mirror made of 492 segments, designed to observe from 0.31 to 28 microns with adaptive optics. Its planned site is Maunakea, Hawaii. Government-level partners include Canada, Japan and India.

Flagship instruments

• 492-segment primary mirror, 30 meters across.
• Adaptive optics across a wavelength range from the near ultraviolet to the mid-infrared.

Recent history

Construction began in 2014 but was halted by Native Hawaiian protests, and Hawaii’s Supreme Court invalidated the building permits in December 2015. In June 2025 the US National Science Foundation chose to advance the Giant Magellan Telescope and not TMT, leaving TMT without US federal construction funding. In September 2026, Physics World reported that members of the TMT International Observatory had turned down Spain’s offer of EUR 1 billion to build on La Palma, leaving Maunakea as the only candidate site.

There are no TMT science results yet. Its science case overlaps with the giant telescopes now under way: exoplanet atmospheres, the first galaxies, and black holes such as the Milky Way’s central one, whose mass was measured from stellar orbits at Keck, TMT’s planned neighbor.

What to watch, 2026-2030

Our sources list no dated TMT milestones. The open questions are funding and the Maunakea site.

Why scientists are watching

Both extremely large telescopes now being built, the ELT and GMT, are in Chile, in the Southern Hemisphere. TMT is the only proposed giant of this class in the Northern Hemisphere, so its fate decides whether northern-sky targets get a 30-meter view in the 2030s.